1. Field of the Invention
The present invention relates generally to rutpurable pressure relieving fluid containers, and more particularly, but not by way of limitation, to fluid containers having rupturable pressure relief areas or members included therein.
2. Description of the Prior Art
A variety of rupturable pressure relieving fluid containers have been developed and used heretofore. For example, aerosol cans and battery cases have included rupturable pressure relief areas or vents which function to relieve excessive fluid pressure from within the cans and cases, such as when the cans or cases become overheated. Other rupturable pressure relief assemblies and devices which contain fluids under pressure until a predetermined high pressure level is exerted thereon have also been developed and used heretofore. For example, assemblies including one or more rupture disks are commonly utilized for over-pressure protection and operate to relieve pressurized fluid therethrough when the pressurized fluid contained thereby reaches a predetermined high or excessive level. The term "container" is used herein to broadly mean any apparatus, assembly or device which includes a fluid pressure rupturable portion or member, or which is capable of including an integral rupturable pressure relief area therein, e.g., rupture disks, rupture disk assemblies, aerosol and other cans for containing pressurized fluids, cases such as battery cases containing materials which can develop pressure upon overheating and other conditions, etc.
Most integral rupturable pressure relief areas heretofore included in containers have involved weakened areas which rupture upon reaching a predetermined pressure level. For example, German Pat. No. 2,336,889 dated Apr. 11, 1974 to Holl discloses a pressurized aerosol container having a concave bottom including a rupturable pressure relief area. That is, a weakened area having a wall thickness considerably thinner than the remainder of the bottom is included therein. The weakened area incorporates either a longitudinal recess or a circumferentially enclosed recess or a recess crossing the area in changing directions. In whatever form the recess takes, the weakened area ruptures and relieves pressurized fluids from the container when the pressure within the container reaches a high level. Such containers and other similar devices generally rupture at widely varying pressures and do not lend themselves to mass production.
A great variety of rupture disks and rupture disk assemblies have been developed and used heretofore for providing positive and controlled overpressure relief. An example of such a rupture disk assembly is described in U.S. Pat. No. 3,834,580 issued Sept. 10, 1984. The assembly includes a concave-convex reverse buckling rupture disk supported between inlet and outlet supporting members. The assembly contains pressurized fluids until a predetermined pressure level is reached whereupon the rupture disk reverses and ruptures to relieve pressure. The rupture disk includes a concave-convex portion having scores thereon creating lines of weakness therein.
The term "score" is used herein to mean an elongated narrow groove or indentation formed on a surface of a rupturable wall portion or disk whereby a corresponding line of weakness is created in the wall or disk. One or more scores can be utilized to form various patterns such as circles, arcs of circles, crosses, etc.
While concave-convex reverse buckling rupture disks have achieved great accuracy and high acceptance, they are susceptible to damage during production, handling or installation which can adversely affect their operation. In low pressure applications, extremely thin material is often required making the disks even more susceptible to damage.
By the present invention, improved rupturable pressure relieving fluid containers such as battery cases, aerosol cans, and rupture disk assemblies are provided which include rupturable frustum-shaped portions. Such rupturable containers allow the use of materials which are generally thicker for a given size and rupture pressure than heretofore possible, are less susceptible to damage, are mass produceable and achieve other advantages as will be apparent from the description which follows.